REFLECTOR: TAS calibration?
Henk van Ooijen
hjvooijen at yahoo.com
Tue Oct 1 12:37:17 CDT 2013
The gradient in wind direction change is the largest in the lower boundaries.
Differs with the roughness of the surface below you.
GPS altitude is not depending on any pressure so a reliable value
Henk
Op 1 okt. 2013, om 18:49 heeft Scott Derrick het volgende geschreven:
> The low pass method, checking your indicated altitude is a fool proof way, you don't have to worry about winds, make a triangle course(preferred over a out and back), etc..
>
> Also remember, an incorrectly calibrated static port will effect your altitude, a dangerous situation if your altimeter is reading higher than you really are!
>
> Scott
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: TAS calibration?
> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Date: 10/01/2013 10:35 AM
>> Thanks for the great article...the guy looks like George Carlin, tho.
>>
>> So, rather than cruising down the runway at low altitude, can't I just fly my plane at a constant GPS altitude and make sure my indicated altitude does not change with air speed? Or, that my TAS matches my GPS average ground speed after two runs with headings 180deg apart?
>>
>> Might head out to the hangar after work and give it a go.
>>
>> Geoff
>>
>>
>>
>> On Tue, Oct 1, 2013 at 12:16 PM, Laurence Coen <lwcoen at hotmail.com> wrote:
>> That is an excellent article. Since I don't think anyone actually believed me in a previous discussion when I said that to determine your TAS, Fly into the wind, record GPS ground speed, fly 180 degrees and take the ground speed and average the two. Read the last sentence in the second paragraph.
>>
>> Larry Coen
>> N136LC
>>
>> From: Henk van Ooijen
>> Sent: Tuesday, October 01, 2013 9:37 AM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: TAS calibration?
>>
>> A nice reading about this from Paul Lipps
>>
>> Regards,
>> Henk van Ooijen
>>
>>
>> Op 1 okt. 2013, om 11:40 heeft Geoff Gerhardt het volgende geschreven:
>>
>>> Dave,
>>>
>>> I have a Dynon Skyview. It does the TAS calculation (using OAT) and reports GPS speed in knots.
>>>
>>> Geoff
>>>
>>>
>>> On Tue, Oct 1, 2013 at 12:23 AM, Dave Philipsen <velocity at davebiz.com> wrote:
>>> I'm just taking another wild stab...are you sure your GPS is reading nautical miles and not statute miles? How is your TAS being calculated? Do you have an EFIS that does it for you or....? Are you estimating OAT or actually measuring it?
>>>
>>> Dave Philipsen
>>> Velocity STD FG
>>> N83DP
>>> On 9/30/2013 4:29 PM, Geoff Gerhardt wrote:
>>>> Mine is a combination pitot static tube. I wonder if I could calibrate it in a similar fashion by putting tape around the pitot tube before or after the static holes.
>>>>
>>>> Dave - yes, I realize that IAS changes with altitude. I am observing an offset between my TAS and GPS ground speed (after accounting for wind).
>>>>
>>>> Geoff
>>>>
>>>>
>>>> On Mon, Sep 30, 2013 at 4:24 PM, Scott Derrick <scott at tnstaafl.net> wrote:
>>>> I have a static port(3 vertical holes, 1/4 inch apart) under the carnard, about a foot, that works well. However it does need to be calibrated. An uncalibrated static port will cause erroneous altitute and IAS indications.
>>>>
>>>> You can calibrate the port by putting a 1/4 inch wide strip of aluminin tape either right ahead of the the hole(s) or right behind them. You can add layers of the tape to increase the effect.
>>>>
>>>> To determine if you need less pressure(tape before the hole) or more pressure(tape after the hole).
>>>>
>>>> Set your altimeter to field elevation, just before departure. Fly at cruise speed, ball in the center, 15-20 ft above the runway. The people on the ground love this! Note your altitude.
>>>>
>>>> If your indicating higher than 20 ft above field elevation, the pressure is too low and you need tape behind the port. If your indicating lower than 20ft above filed elevation, the pressure is too high and you need tape ahead of the port.
>>>>
>>>> If your within 50 ft, your good to go. I did this after I bought my plane, it was off 300ft. and after I painted, again off 300ft. The tape lasts forever and looks like an embedded metal strip.
>>>>
>>>> my $.002, works for me.
>>>>
>>>> Scott
>>>>
>>>> -------- Original Message --------
>>>> Subject: Re: REFLECTOR: TAS calibration?
>>>> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
>>>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>>> Date: 09/30/2013 01:56 PM
>>>>> Guys,
>>>>>
>>>>> My pitot/static is positioned under the canard - I suspect it is seeing increased pressure at high speeds thus giving me a low indicated airspeed. This weekend, I thought I was smart and put a small static port right ahead of the dog house thinking that was a great place. After a quick flight where my air speeds were through the roof, I realized that that spot was actually doing the opposite and was creating a low pressure region as the air bends over the nose. I see now that I need to find a place on the flat section of the fuselage to put the static port.
>>>>>
>>>>> Where does everyone else have their static port?
>>>>>
>>>>> Thanks.
>>>>>
>>>>> Geoff
>>>>>
>>>>>
>>>>> On Sun, Sep 29, 2013 at 11:43 AM, Kurt Winker <nmflyer1 at aol.com> wrote:
>>>>> Sounds like a trip-strip may be in order.
>>>>>
>>>>> Kurt
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>> > On Sep 29, 2013, at 6:47, Scott Baker <scottb33333 at gmail.com> wrote:
>>>>> >
>>>>> > I would assume that you are factoring altitude and temperature when calculating TAS. If so, airspeed error might be related to a pressurization of the static system (a common problem in Velocity aircraft that have their static port located forward of the entry door).
>>>>> >
>>>>> > Scott Baker
>>>>> >
>>>>> >> On Sep 28, 2013, at 8:29 PM, Geoff Gerhardt <geoff.gerhardt at gmail.com> wrote:
>>>>> >>
>>>>> >> Guys,
>>>>> >>
>>>>> >> Flying today I realized that my ground speed seems to be always greater than my TAS. I figured at least some of the time it should be less (i.e. into a headwind). But it always seemed to be greater. So, today, I flew in a box, E, W, N, S and recorded my TAS and GS. My TAS was constant at 159ktas on each leg, and my GS (GPS) was 185, 179, 171, 175 for the W, N, E, S legs. If I add all those up and divide by four, I get 177.5kts, yet my TAS registered 158ktas. Am I missing something? Is my airspeed indicator reading too low?
>>>>> >>
>>>>> >> Thanks.
>>>>> >>
>>>>> >> Geoff
>>>>> >>
>>>>> >> _______________________________________________
>>>>> >> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>>> >>
>>>>> >> Visit the gallery! www.tvbf.org/gallery
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>>>>> >> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>> >
>>>>> > _______________________________________________
>>>>> > To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>>> >
>>>>> > Visit the gallery! www.tvbf.org/gallery
>>>>> > user:pw = tvbf:jamaicangoose
>>>>> > Check new archives: www.tvbf.org/pipermail
>>>>> > Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>>
>>>>> _______________________________________________
>>>>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>>>
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>>>>> Check new archives: www.tvbf.org/pipermail
>>>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>>>
>>>>> Visit the gallery! www.tvbf.org/gallery
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>>>>> Check new archives: www.tvbf.org/pipermail
>>>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>
>>>> --
>>>> Even if you're on the right track, you'll get run over if you just sit there.
>>>> Will Rogers
>>>>
>>>> _______________________________________________
>>>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>>
>>>> Visit the gallery! www.tvbf.org/gallery
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>>>> Check new archives: www.tvbf.org/pipermail
>>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>>
>>>> Visit the gallery! www.tvbf.org/gallery
>>>> user:pw = tvbf:jamaicangoose
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>>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>
>>>
>>> _______________________________________________
>>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>>
>>> Visit the gallery! www.tvbf.org/gallery
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>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
>>
>> A nice reading about this from Paul Lipps
>>
>> Regards,
>> Henk van Ooijen
>>
>>
>> Op 1 okt. 2013, om 11:40 heeft Geoff Gerhardt het volgende geschreven:
>>
>>
>> > Dave,
>> >
>> > I have a Dynon Skyview. It does the TAS calculation (using OAT) and reports GPS speed in knots.
>> >
>> > Geoff
>> >
>> >
>> > On Tue, Oct 1, 2013 at 12:23 AM, Dave Philipsen <velocity at davebiz.com> wrote:
>> > I'm just taking another wild stab...are you sure your GPS is reading nautical miles and not statute miles? How is your TAS being calculated? Do you have an EFIS that does it for you or....? Are you estimating OAT or actually measuring it?
>> >
>> > Dave Philipsen
>> > Velocity STD FG
>> > N83DP
>> > On 9/30/2013 4:29 PM, Geoff Gerhardt wrote:
>> >> Mine is a combination pitot static tube. I wonder if I could calibrate it in a similar fashion by putting tape around the pitot tube before or after the static holes.
>> >>
>> >> Dave - yes, I realize that IAS changes with altitude. I am observing an offset between my TAS and GPS ground speed (after accounting for wind).
>> >>
>> >> Geoff
>> >>
>> >>
>> >> On Mon, Sep 30, 2013 at 4:24 PM, Scott Derrick <scott at tnstaafl.net> wrote:
>> >> I have a static port(3 vertical holes, 1/4 inch apart) under the carnard, about a foot, that works well. However it does need to be calibrated. An uncalibrated static port will cause erroneous altitute and IAS indications.
>> >>
>> >> You can calibrate the port by putting a 1/4 inch wide strip of aluminin tape either right ahead of the the hole(s) or right behind them. You can add layers of the tape to increase the effect.
>> >>
>> >> To determine if you need less pressure(tape before the hole) or more pressure(tape after the hole).
>> >>
>> >> Set your altimeter to field elevation, just before departure. Fly at cruise speed, ball in the center, 15-20 ft above the runway. The people on the ground love this! Note your altitude.
>> >>
>> >> If your indicating higher than 20 ft above field elevation, the pressure is too low and you need tape behind the port. If your indicating lower than 20ft above filed elevation, the pressure is too high and you need tape ahead of the port.
>> >>
>> >> If your within 50 ft, your good to go. I did this after I bought my plane, it was off 300ft. and after I painted, again off 300ft. The tape lasts forever and looks like an embedded metal strip.
>> >>
>> >> my $.002, works for me.
>> >>
>> >> Scott
>> >>
>> >> -------- Original Message --------
>> >> Subject: Re: REFLECTOR: TAS calibration?
>> >> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
>> >> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>> >> Date: 09/30/2013 01:56 PM
>> >>> Guys,
>> >>>
>> >>> My pitot/static is positioned under the canard - I suspect it is seeing increased pressure at high speeds thus giving me a low indicated airspeed. This weekend, I thought I was smart and put a small static port right ahead of the dog house thinking that was a great place. After a quick flight where my air speeds were through the roof, I realized that that spot was actually doing the opposite and was creating a low pressure region as the air bends over the nose. I see now that I need to find a place on the flat section of the fuselage to put the static port.
>> >>>
>> >>> Where does everyone else have their static port?
>> >>>
>> >>> Thanks.
>> >>>
>> >>> Geoff
>> >>>
>> >>>
>> >>> On Sun, Sep 29, 2013 at 11:43 AM, Kurt Winker <nmflyer1 at aol.com> wrote:
>> >>> Sounds like a trip-strip may be in order.
>> >>>
>> >>> Kurt
>> >>>
>> >>> Sent from my iPhone
>> >>>
>> >>> > On Sep 29, 2013, at 6:47, Scott Baker <scottb33333 at gmail.com> wrote:
>> >>> >
>> >>> > I would assume that you are factoring altitude and temperature when calculating TAS. If so, airspeed error might be related to a pressurization of the static system (a common problem in Velocity aircraft that have their static port located forward of the entry door).
>> >>> >
>> >>> > Scott Baker
>> >>> >
>> >>> >> On Sep 28, 2013, at 8:29 PM, Geoff Gerhardt <geoff.gerhardt at gmail.com> wrote:
>> >>> >>
>> >>> >> Guys,
>> >>> >>
>> >>> >> Flying today I realized that my ground speed seems to be always greater than my TAS. I figured at least some of the time it should be less (i.e. into a headwind). But it always seemed to be greater. So, today, I flew in a box, E, W, N, S and recorded my TAS and GS. My TAS was constant at 159ktas on each leg, and my GS (GPS) was 185, 179, 171, 175 for the W, N, E, S legs. If I add all those up and divide by four, I get 177.5kts, yet my TAS registered 158ktas. Am I missing something? Is my airspeed indicator reading too low?
>> >>> >>
>> >>> >> Thanks.
>> >>> >>
>> >>> >> Geoff
>> >>> >>
>> >>> >> _______________________________________________
>> >>> >> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >>> >>
>> >>> >> Visit the gallery! www.tvbf.org/gallery
>> >>> >> user:pw = tvbf:jamaicangoose
>> >>> >> Check new archives: www.tvbf.org/pipermail
>> >>> >> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> >>> >
>> >>> > _______________________________________________
>> >>> > To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >>> >
>> >>> > Visit the gallery! www.tvbf.org/gallery
>> >>> > user:pw = tvbf:jamaicangoose
>> >>> > Check new archives: www.tvbf.org/pipermail
>> >>> > Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> >>>
>> >>> _______________________________________________
>> >>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >>>
>> >>> Visit the gallery! www.tvbf.org/gallery
>> >>> user:pw = tvbf:jamaicangoose
>> >>> Check new archives: www.tvbf.org/pipermail
>> >>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> >>>
>> >>>
>> >>>
>> >>> _______________________________________________
>> >>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >>>
>> >>> Visit the gallery! www.tvbf.org/gallery
>> >>> user:pw = tvbf:jamaicangoose
>> >>> Check new archives: www.tvbf.org/pipermail
>> >>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> >>
>> >> --
>> >> Even if you're on the right track, you'll get run over if you just sit there.
>> >> Will Rogers
>> >>
>> >> _______________________________________________
>> >> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >>
>> >> Visit the gallery! www.tvbf.org/gallery
>> >> user:pw = tvbf:jamaicangoose
>> >> Check new archives: www.tvbf.org/pipermail
>> >> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> >>
>> >>
>> >>
>> >> _______________________________________________
>> >> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >>
>> >> Visit the gallery! www.tvbf.org/gallery
>> >> user:pw = tvbf:jamaicangoose
>> >> Check new archives: www.tvbf.org/pipermail
>> >> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> >
>> >
>> > _______________________________________________
>> > To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> >
>> > Visit the gallery! www.tvbf.org/gallery
>> > user:pw = tvbf:jamaicangoose
>> > Check new archives: www.tvbf.org/pipermail
>> > Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
>>
>> _______________________________________________
>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery! www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
>> _______________________________________________
>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery! www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
>>
>>
>> _______________________________________________
>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery! www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>
> --
> He who knows others is wise;
> He who know himself is enlightened.
> Lao-tzu
> _______________________________________________
> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery! www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
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